Large mirror lamps (e.g., as disclosed in German Patent No. DE 197 29 758 A1) have the disadvantage that they include obstacles in the illumination field, which impair the shape of the illumination field, because a path between the light emitting surface of the lamp and the illumination field is interrupted by the obstacle. In resolved light systems (e.g., as disclosed in German Patent “Gebrauchsmuster” No. DE 84 05 380 U1), individual smaller light emitting surfaces suffer from an loss in illuminance through shadows cast by the operating surgeon. Furthermore, prior art operating lamps do not provide for a change of shape of the illumination field depending on the application (the area illuminated on the operating table).